It is known that ingestion of particulates such as sand or other debris, such as dry leaves, dust, and the like, from the environment into internal combustion engines result in engine damage requiring frequent repairs. For example, in desert environments where loose dry sand prevails, helicopter engines deteriorate at a much faster rate, due in large part to ingestion of sand and other small foreign objects.
Typically, for example, helicopter engines are protected by a variety of different methods, including conventional inertial inlet particle separators that separate particulates from air. An example of these separators 10 is shown in cross section along the path of airflow in FIG. 1. The separator 10 has a separator body 12 that has an air inlet end 14. Upon entering the inlet end 14 and flowing towards the engine (not shown) the incoming particulate-containing air, shown by arrows 30, passes through an arcuate portion 16 of the separator body 12. In the arcuate portion 16, the air flow rate is accelerated because the internal cross sectional area for flow is reduced, and the air 30 is forced to follow the arcuate curvature of portion 16. The acceleration of the airflow 30 as it follows the arcuate flow path causes particulates to separate away from the arcuate portion 16 and towards an opposite side 18. Accordingly, the particulates in incoming air 30 tend to concentrate in region 32 closer to portion 18. Thus, particulates are concentrated into a “dirtier air” 32 region. Cleaner air from which particulates have migrated, tend to concentrate in a “clean air” region 34 closer to portion 16. A splitter 35 is interposed selectively between the dirty air region 32 and the clean air region 34 to separate the airflow into two streams. The dirty air 36 is then routed to the environment while the cleaned air 38 flows to the engine inlet for supporting combustion of fuel.
Under environmental conditions where dust, sand and other particulates are present in unusually high concentrations in the air, the separation efficiency of such inertial particle separators is not adequate to protect engines. Frequent engine overhauls are necessary as a consequence of particulate damage. Engines in equipment other than helicopters often suffer from the same particulate-related damage.
Installation losses (e.g. in intake air total pressure) and space-efficient packaging are important issues in the protection of engines from particulate erosion. Currently the most compact, lowest-weight system of foreign object damage protection is an inertial inlet particle separator. When higher efficiency particulate separation is required, other systems, such as vortex tubes and barrier filters, may be used in conjunction with an inertial inlet particle separator. However, these other systems come with substantial installation losses, weight increases and attendant aircraft performance penalties.
Accordingly, it is desirable to provide a high efficiency engine inlet air particulate separator to separate particulates from incoming air to be charged to combustion engines. In addition, it is desirable that the separator be easily retrofitted to existing equipment and resistant to clogging by separated particulates. For certain applications, light weight and/or compact packaging are also desirable. Furthermore, other desirable features and characteristics of the high efficiency particulate separators will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.